1. Field of the Invention
The present invention relates to a lens apparatus in which a drive unit driving a magnification-varying lens unit is disposed outside a barrel that houses the magnification-varying lens unit and a focus lens unit.
2. Description of the Related Art
Some lens apparatuses separate a part of a light beam from an object directed to an imaging surface by a reflecting element such as a half mirror or a total reflecting mirror to guide it to a focus detection sensor and detects a focus state of an imaging optical system based on a phase difference obtained by the focus detection sensor (Japanese Patent Laid-open No. 55-76312).
A lens apparatus disclosed in Japanese Patent Laid-open No. 55-76312 includes a focus detection optical system which guides a light beam reflected by a reflecting element to the focus detection sensor different from the imaging optical system. The focus detection optical system and the focus detection sensor are disposed so as to protrude to an outside of a barrel which houses the imaging optical system.
However, the lens apparatus disclosed in Japanese Patent Laid-open No. 55-76312 has a problem as described below.
In a portable lens apparatus for a television broadcast, a user mostly uses a manual focus and an auto focus (AF) concomitantly. The manual focus is performed by rotating an operation ring which is rotatably provided at an outer circumference of a barrel. Similarly, the operations of varying a magnification or an iris (an aperture) are mostly performed by the operation of the operation ring.
However, when the focus detection optical system and the focus detection sensor are protruded outside the barrel, a hand which operates each operation ring may be interfered with by the protruded portion. In this case, the operability of each operation ring is deteriorated, and an accurate and quick operation cannot be performed.
When foreign substances such as dirt are adhered to the focus detection sensor, an output from the sensor, i.e. a focus detection result, may have an error. Therefore, an enclosure needs to be provided around the sensor for preventing the dirt. However, since the sensor is disposed at an end portion of the focus detection optical system, the protruded portion is enlarged if such an enclosure is provided. Thus, the operability of the manual operation is deteriorated.